The present invention relates to subterranean operations and, more particularly, to a method and system for monitoring a coiled tubing.
Hydrocarbons, such as oil and gas, are commonly obtained from subterranean formations that may be located onshore or offshore. The development of subterranean operations and the processes involved in removing hydrocarbons from a subterranean formation are complex. Typically, subterranean operations involve a number of different steps such as, for example, drilling a wellbore at a desired well site, treating the wellbore to optimize production of hydrocarbons, and performing the necessary steps to produce and process the hydrocarbons from the subterranean formation.
When performing subterranean operations, it is often desirable to be aware of the characteristics of the formation being developed as well as various parameters reflecting the status of the particular operation being performed downhole. For instance, it may be desirable to know temperature, pressure, flow rate, resistivity, and other formation parameters.
In order to facilitate transfer of power, data and materials associated with the performance of subterranean operations, coiled tubing may be inserted into the wellbore. Coiled tubing is typically a metal piping whose diameter may vary depending on the particular application. In order to facilitate transmission of data signals, control signals, power signals, etc., cables of varying diameters may be directed downhole through the coiled tubing. Typically, the cables may be anchored into the coiled tubing with a system that permits them to tear away from the anchor if the cable tension approaches the yield strength of the cable.
In addition to cables, coiled tubing may be used to direct fluids associated with performance of subterranean operations into or out of the wellbore. Fluid flow through the coiled tubing may impact the positioning of the cables therein. Once the cables have moved out of their intended position, an operator may reposition them, for instance through reverse circulation. The term reverse circulation as used herein refers to either directing a suitable fluid downhole through the annulus between the coiled tubing and the wellbore (or the casing if the wellbore is cased) and back up through the coiled tubing or circulating fluid from the bottom to the top of the coiled tubing once it has been retrieved and stored on the reel assembly at the surface. The upward flow of fluids through the coiled tubing may then reposition the cables located therein through the application of frictional drag.
Accordingly, over time, a user may come up with conservative numbers for how many runs and at what flow rate, the system can be utilized before the cable “overstuff” needs to be repositioned through reverse circulation. The term “overstuff” as used herein refers to the length of cable inside the coiled tubing that exceeds the total length of the coiled tubing string. However, changes in fluid chemistry, flow rate, pumping time, depth and hole geometry can all affect how quickly the overstuff is moved to the bottom of the coil. It is therefore desirable to develop a method and system to monitor the position of cables within a coiled tubing in real-time without having to take the coiled tubing unit out of service.